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The concept of harnessing energy from moving water and the wind continues to be the source of research and innovation. The most common method used to harness energy from moving water involves building a hydroelectric dam and extracting energy by passing water through turbines. Building dams creates problems, including flooding of land, creating barriers to migrating fish and upsetting the natural high and low water flow cycles. Windmills are commonly used for harnessing wind energy. Windmills typically have a number of blades, wings or other fluid foils that rotate about a central, typically horizontally-oriented, drive shaft. Another type of energy-harnessing apparatus is a conveyor-type apparatus in which a number of fluid foils are carried by an endless chain passing between spaced-apart sprockets. Conveyer-type apparatus have been developed for use in both air and water. Some of these apparatus use flexible fabric as the fluid foils; see, for example, U.S. Pat. No. 443,641. Other conveyor-type apparatus use relatively rigid fluid foils; see U.S. Pat. Nos. 1,502,296; 4,049,300; and 4,563,168.
The present invention is directed to a conveyor-type fluid energy-harnessing apparatus in which reversible fluid foils permit energy to be extracted from the moving fluid along the upstream reach and the downstream reach in a simple and effective manner. The invention may also be used in, for example, tidal flow areas in which the direction of movement of the water periodically reverses itself without the need for changing the orientation of the apparatus.
A first aspect of the invention is directed to a conveyor-type apparatus for harnessing energy from a fluid flow, for example a river, comprising a support structure, a continuous-loop, flexible driven element, for example a pair of chains, mounted to the support structure and extending along a closed-loop path, the path defining an interior region and an exterior region, and a series of reversible fluid foils. The driven element has first and second reaches, the first and second reaches being upflow and downflow reaches when fluid flows from the first reach to the second reach. Each fluid foil comprises first and second sides and is connected to the flexible driven element for movement between a first orientation, situated in the interior region when moving along the upflow reach, and a second orientation, situated in the exterior region when moving along the downflow reach. The first sides of the fluid foils are generally concave when moving along the upflow reach and generally convex when moving along the downflow reach. The second sides are generally concave when moving along the downflow reach and generally convex when moving along the upflow reach. The driven element may be coupled to, for example, an electrical generator to harness energy from the fluid flow.
A second aspect of the invention is directed to method for harnessing energy from a fluid flow. A conveyor-type fluid energy apparatus is positioned at a fluid flow site. The apparatus comprises a support structure, a continuous-loop, flexible driven element mounted to the support structure and extending along a closed-loop path, the path defining an interior region and an exterior region and a series of reversible fluid foils movably connected to the flexible driven element. The driven element has first and second reaches as it moves along the path, said first and second reaches being upflow and downflow reaches when fluid flows from the first reach to the second reach. The driven element is oriented so that the upflow reach is transverse to a fluid flow direction. The fluid foils and the driven element therewith are driven along the upflow reach in a first closed-loop path direction, the fluid foils being driven by the fluid flow with the fluid foils situated in the interior region in a first orientation. The fluid foils move from the first orientation to a second orientation as the fluid foils move along a first transition region along the path from the upstream reach to the downstream reach. The fluid foils and the driven element therewith are driven along the downflow reach in the first closed-loop path direction, the fluid foils being driven by the fluid flow with the fluid foils situated in the exterior region when in the second orientation. The fluid foils move from the second orientation to the first orientation as the fluid foils move along a second transition region along the path from the downstream reach to the upstream reach. The driven element may therefore be coupled to, for example, an electrical generator to harness energy from the fluid flow.
The present invention finds particular utility for harnessing energy from river or tidal flows. The fluid foils may act like series of sails as they move along the upflow reach and the downflow reach and are driven by the fluid flow along both reaches. The series of fluid foils are preferably submerged below the surface of the water so that floating debris passes over the apparatus as opposed to being snagged in the apparatus. The apparatus may be designed so that it can be towed to optimum water flow locations without the need for a barge or complicated procedures for transporting the apparatus. The apparatus can be designed to be, for example, supported on the bottom of a river or suspended from floating pontoons or other appropriate structures. The invention is suitable for use in even relatively shallow waterways.
Other features and advantages of the invention will appear from the following description in which the preferred embodiments have been set forth in detail in conjunction with the accompanying drawings.